G9 Revision Checklist
I’m happy with this / I need help with thisG9
/The wave model of radiation
1. / What do waves do, and what types of waves are there?- recognise that a wave consists of disturbances that transfer energy in the direction that the wave travels, without transferring matter;
2. / Does frequency or amplitude affect the speed of waves?
- recall that the frequency of the waves, in hertz (Hz), is the number of waves each second that are made by the source, or that, for example, pass through any particular point in the medium;
- recall that the wavelength of the waves is the distance between the same point on two adjacent disturbances;
- recall that the amplitude of the waves is the distance between the crest, or trough, of a wave and its undisturbed position.
- draw and/or interpret diagrams showing the amplitude and the wavelength of water waves.
- state and be able to use the equation
(metres per second, m/s)(hertz, Hz)(metres, m)
Rearrangement of the equation is only expected on higher tier.
recognise that the speed of waves is affected very little, if at all, by the frequency or the amplitude of the waves.
3. / Do sound and light behave like water waves?
What does this tell us about sound and light?
- draw and interpret diagrams showing the reflection of plane water waves and narrow beams of sound or light from a plane reflector.
- recognise that wave speed is affected by what waves are travelling along or through (the medium);
- recall that refraction involves the change in speed of a wave;
- explain how changing the speed of a wave causes a change in wavelength since the frequency of the waves cannot change, and that this may cause a change in direction;
- draw and/or interpret diagrams showing the refraction of plane water waves when they cross into water of a different depth due to the change in speed;
- draw and/or interpret diagrams showing the refraction of beams of light or sound when they cross the boundary between different media;
4. / Is there invisible radiation beyond the ends of the spectrum?
- recall that the different colours of light in the spectrum have different frequencies and wavelengths;
5. / In what ways are electromagnetic waves different from other types of waves?
- recall that all types of electromagnetic radiation travel at exactly the same, very high, speed through space (a vacuum);
6. / Which electromagnetic waves are suited to different uses and why?
- appreciate that different wavelengths of electromagnetic radiation are used for different purposes due to the difference in reflection, absorption or transmission by different materials to include:
some wavelengths of microwaves travel particularly well through the atmosphere, so they can be used to carry information to and from satellites;
other wavelengths of microwaves are strongly absorbed by water molecules, so they can be used for cooking;
satellite dishes and microwave oven cases are made of metal because metals reflect microwaves well;
light and infrared radiation can be used to carry information along optical fibres because they travel through without significant loss;
infrared radiation is absorbed by most solid materials which makes it useful for grills and toasters and in remote controls for TVs and VCRs;
X-rays do not pass very easily through dense materials, so they can be used to produce shadow pictures of bones in our bodies or of metal objects in aircraft passengers’ luggage.
when radio waves meet a metal aerial, they produce electrical waves which can be fed into a receiver.
7. / How can waves be made to carry information?
- appreciate that signals can be carried not only by radio waves and microwaves through the Earth’s atmosphere and through space but also by light waves and infrared waves through optical fibres.
- recognise that if a wave is to carry information the waves must be made to vary in amplitude or frequency, and that the information is carried by the pattern of the variation;
- interpret diagrams showing how a sound wave can be used to vary the amplitude of a radio wave, with a pattern that matches its own frequency;
- appreciate that because the signal carried by the radio waves varies in exactly the same way as the information it is carrying it is called an analogue signal.
- recognise that the job of the receiver is to reproduce the original sound from the pattern of the variation;
8. / What are digital signals?
- recall that sound (or other information) can be transmitted digitally (digital signal);
- recall that the sound is converted into a digital code made up from just two symbols (0 and 1);
- recall that the coded information is used to control the short bursts of waves (pulses) produced by a source of waves (0 = no pulse, 1 = pulse);
9. / When sending information over long distances, why is the quality better using digital signals?
- appreciate that an important advantage of digital signals over analogue signals is their higher quality, because the information carried by the signal is less affected by the transmission process;
- appreciate that as signals travel, they become weaker;
- recall that random additions to the original signal (noise) may be picked up as the signal travels;
- recall each time the signal is amplified, any noise that has been picked up is also amplified;
- understand that this means that the signal becomes less and less like the original signal, so its quality deteriorates;
- understand that, with digital signals, even though pulses weaken with distance, they are still recognised as ‘on’ states, whereas noise is generally of low amplitude and is ignored (i.e. interpreted as ‘off’;